For future readers please use this project on my github, it includes a full screen preview on almost all devices as well. The previous answer was not a solid implementation but more of a quick solution. The github repository contains all the changes and check the changelog as well.

I have found a work around, not very secure but it's something right. Firstly if you go to the BarcodeCaptureActivity.java the onTap() gets the last barcode detected right and wraps the barcode object into an intent. While all the BarcodeGraphicTracker.java tracks the positions of any Barcode objects. So if you could use any of the two methods onNewItem() or onUpdate() you can easily send the barcode data to the calling activity using intents.

Now how i did this, since the BarcodeGraphicTracker is just a normal class:

1.Create a class that holds an static activity variable:

public class ActivitySource {
public static Activity caller;
}

In BarcodeCaptureActivity.java under the onCreate() add:

ActivitySource.caller = this;

In BarcodeGraphicTracker under the onNewItem(int id, Barcode item) add the following under mGraphic.setId(id);